Preparation of Pincer Hafnium Complexes for Olefin Polymerization

• Published in: Molecules (Basel, Switzerland) Switzerland), 2019-04, Vol.24 (9), p.1676
• Main Authors: Kwon, Su Jin, Baek, Jun Won, Lee, Hyun Ju, Kim, Tae Jin, Ryu, Ji Yeon, Lee, Junseong, Shin, Eun Ji, Lee, Ki Soo, Lee, Bun Yeoul
• Format: Article
• Language: English
• Subjects: Alkenes - chemistry; Catalysis; Catalysts; Crystallography; Crystallography, X-Ray; Hafnium; Hafnium - chemistry; hafnium complex; Ion pairs; Ligands; Magnetic Resonance Spectroscopy; Models, Molecular; Molecular Structure; olefin polymerization; pincer complex; Polymerization; Polymers - chemical synthesis; Polymers - chemistry; Polyolefins; post-metallocene; Precursors; Pyridines; X-ray crystallography
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules24091676

Pincer-type [C , N , N ]HfMe complex is a flagship among the post-metallocene catalysts. In this work, various pincer-type Hf-complexes were prepared for olefin polymerization. Pincer-type [N , N , N ]HfMe complexes were prepared by reacting in situ generated HfMe with the corresponding ligand precursors, and the structure of a complex bearing 2,6-Et C H N moieties was confirmed by X-ray crystallography. When the ligand precursors of [(CH )R Si-C H N-C(H)PhN(H)Ar (R = Me or Ph, Ar = 2,6-diisopropylphenyl) were treated with in situ generated HfMe , pincer-type [C , N , N ]HfMe complexes were afforded by formation of Hf-CH Si bond. Pincer-type [C , S , N ]HfMe complex, where the pyridine moiety in the flagship catalyst was replaced with a thiophene unit, was not generated when the corresponding ligand precursor was treated with HfMe . Instead, the [S , N ]HfMe -type complex was obtained with no formation of the Hf-C bond. A series of pincer-type [C , N , N ]HfMe complexes was prepared where the arylamido moiety in the flagship catalyst was replaced with alkylamido moieties (alkyl = iPr, cyclohexyl, Bu, adamantyl). Structures of the complexes bearing isopropylamido and adamantylamido moieties were confirmed by X-ray crystallography. Most of the complexes cleanly generated the desired ion-pair complexes when treated with an equivalent amount of [(C H ) N(H)Me] [B(C F ) ] , which showed negligible activity in olefin polymerization. Some complexes bearing bulky substituents showed moderate activities, even though the desired ion-pair complexes were not cleanly afforded.